Japanese patent laid-open No. 2014-119513 discloses an invention regarding a fusion splicer. According to this invention, optical fibers are put on the fiber holding parts of a fusion splicer, and thereafter its windbreak cover is closed, the optical fibers are fusion-spliced by electric arc, the fusion spliced portion is subjected to a tensile test (proof test) upon end of the electric arc, and finally, the spliced optical fiber is taken out by opening the windbreak cover.